While research in the area of emotional numbing in PTSD is growing, there are considerable gaps in our current knowledge of its underlying processes. One of the current debates in this literature focuses on whether emotional numbing is automatically controlled and occurs outside of conscious processing or whether there are strategic aspects to the symptoms and there exists some conscious control over when numbing is used. Emotional and psychophysiological studies have shown that emotion regulation aspects of PTSD can be reliably examined while individuals are presented with positive and negative images. In a series of two studies, I will examine emotional and physiological responding associated with emotional numbing, the automatic or strategic nature of emotional numbing, and how emotional numbing is related to treatment response. In Study 1, I will seek to directly manipulate emotional numbing responses using four samples: PTSD, trauma-exposed no PTSD, panic disorder, and no psychopathology controls. During emotional manipulation instructions (emotional numbing, express emotion, no instruction), participants will be presented with affective images (positive, negative, neutral), and both emotional and psychophysiological responses will be measured. In Study 2, I will furthermore examine emotional numbing pre- and post- treatment, comparing treatment modality (prolonged exposure vs. sertraline) and treatment response. [unreadable] [unreadable] [unreadable]